//70.爬楼梯
//https://leetcode.cn/problems/climbing-stairs/
class Solution {
public:
    int climbStairs(int n) {
        //类似于斐波那契数
        int n1 = 0,n2 = 0,n3 = 1;
        for(int i = 0;i<n;++i)
        {
            n1 = n2;
            n2 = n3;
            n3 = n1+n2;
        }
        return n3;
    }
};